Protective cap for infrared radiation thermometer

ABSTRACT

The invention is directed to a protective cap ( 2 ) for a temperature measurement probe ( 30 ) of an infrared radiation thermometer ( 1 ) that can be introduced into a body cavity ( 31 ). The protective cap ( 2 ) is comprised of a base body ( 12 ) shaped to fit the body cavity ( 31 ) and having a window ( 15 ) transparent to infrared radiation. The base body ( 12 ) is provided with additional structures ( 13; 18, 20 ) at least in parts to improve heat insulation between the temperature measurement probe ( 30 ) and the body cavity ( 31 ). This heat insulation of the temperature measurement probe ( 30 ) prevents measurement errors by the infrared radiation thermometer ( 1 ).

This is a continuation of application application Ser. No. 09/117,724,filed on Aug. 5, 1998 now U.S. Pat. 6,634,787.

This invention relates to a protective cap for an infrared radiationthermometer according to the prior-art portion of patent claim 1.

Infrared radiation thermometers are used for measuring body temperature.Typically, such a radiation thermometer includes a housing with a windowadmitting radiation, an internal optic system and an infrared sensorthat is associated with an evaluation unit. The window admittingradiation serves to close off the interior of the housing of theradiation thermometer, thereby protecting the optic system and thesensor from contamination and destruction.

As an additional protection, protective caps of the type initiallyreferred to are seated onto the end of the thermometer; such protectivecaps are described, for example, in EP-B1-0 201 790, U.S. Pat. No.5,179,936 or U.S. Pat. No. 5,293,862. These protective caps not onlyserve the function of protecting the infrared transmitting window, butalso are intended to prevent the transmission of diseases to the user,which is accomplished in that a new protective cap is installed prior toeach temperature being taken or prior to each measurement—and this alsoin cases where different persons are involved. The disposable speculumas referred to in EP-B1-0 201 790, U.S. Pat. No. 5,179,936 or U.S. Pat.No. 5,293,862 is fitted over the ear canal probe of a tympanicthermometer that is sensitive to infrared radiation, this disposablespeculum having an infrared transmitting membrane made of polypropyleneor polyethylene. The portion carrying the membrane is aninjection-molded part.

To determine a person's body temperature, the forward end of thetemperature measurement probe is inserted into the ear. The infraredradiation emitted by the tympanic membrane and by the ear canal entersthe thermometer through the window and is incident, via the optic systemor an optical waveguide and an interference filter, on the infraredsensor. The increase in temperature produced in the sensor results in anelectrical output voltage from which the radiation temperature can bedetermined by means of an evaluation unit.

In such devices it has however shown that during measurement atemperature gradient occurs within the thermometer's optic system due tocontact of the ear with the thermometer's generally cooler optic system,from which gradient a measurement error results usually. Moreover, theear canal is subject to cooling by the thermometer. Because thethermometer detects also the infrared radiation of the ear canal or someother body cavity receiving the radiation thermometer, a further sourceof error results.

Proceeding from the state of the art referred to in the foregoing andthe attendant problems of potential measurement errors, it is an objectof the present invention to provide a protective cap protecting the userof such an infrared thermometer against the transmission of diseases, inaddition to preventing the thermometer's optic system fromcontamination. It is a still further object to avoid or at leastsubstantially reduce the measurement errors of the type described in theforegoing that occur with conventional clinical thermometers equippedwith protective cap.

In a protective cap of the type initially described, the foregoingobject is attained according to a first invention by the characterizingfeatures of claim 1. Additional structures provide for insulation ofprecisely that portion of the base body that is in the immediatevicinity of the window and hence in intimate contact with the wall ofthe body cavity as, for example, the ear canal, in such fashion that inthis particular portion the transfer of heat to the infrared opticsystem is reduced or maintained at such a low level as to be negligibleas regards its effect on the temperature measurement. Because thethermal insulation of the protective cap reduces the passage of heatoutside the window, the cooling of, for instance, the ear canal is alsodiminished at the same time. This has the further effect that by reasonof the diminished cooling effect on the ear the user has the impressionthat the thermometer with this protective cap is warmer and hencesubstantially less discomforting.

Further, this thermally insulative means may be of a soft configuration,being more pleasant in the ear than a firm, non-pliant material or aprotective cap sheathed with such a material. A further particularadvantage of such a protective cap is to use it in conjunction with aclinical thermometer having a small probe tip. A clinical thermometerwith a small probe tip is suitable for taking both an adult's and achild's temperature if the protective cap of thermally insulatingmaterial is made available in at least two sizes. However, such aprotective cap may also be fabricated from a particularly soft,thermally insulating and hence elastic material which conforms itself toboth an adult's and a child's ear canal, in spite of the sizedifference. According to the present invention, protective caps of thistype are typically utilized as disposable protective caps.

To enable ease and nevertheless accuracy of positioning of theprotective cap in the ear canal, but also to avoid different thermaleffects due to different positions, at least the base body's outersurface that comes into contact with the ear canal or also the basebody's entire outer surface outside the window area should be providedwith the thermally insulative means. Such a configuration of the surfaceof the protective cap ensures at all times an adequate thermalinsulation against the temperature measurement probe in the differentpositions of the clinical thermometer.

A further possibility for increasing the thermal insulation of thetemperature measurement probe of the radiation thermometer includesproviding the entire base body outside the window with thermallyinsulative means, that is, not only its outside but also its inside.With such an approach it is possible to prevent the thickness of theouter layer on the base body of thermally insulative means from becomingexcessively thick, in addition to enabling the thermally insulativemeans on the inside to be dimensioned and set to an elasticity in suchfashion as to achieve at the same time a clamping and yet detachablemounting of the protective cap on the end of the radiation thermometer.

The base body may at the same time serve as a stable support for thethermally insulating material which is affixed at least on the outside.A soft, porous foamed plastic material is preferably used as thethermally insulative means of the additional structure (claim 2).

Another preferred possibility resides in that the additional structureaccording to claim 3 is a body that is formed of one or several airchambers.

The features of claim 4, enhance the thermal insulation effect stillfurther. Preferably, in the protective cap structure comprising one orseveral air chambers, a flexible outer film is applied to the outsideclaim 5). Such an outer film forms at the same time a smooth outersurface offering little possibility for contaminants to collect anddeposit during storage and stockkeeping of the protective caps.

As flexible outer film materials bounding, for instance, the air chamberor the air chambers of a thermally insulative means, polypropylene (PP),polyvinyl or polyethylene (PE) are proposed (claim 6). For one thing,these are low-cost materials, for another thing, they are easy toprocess in order to manufacture the thermally insulating bodies, andmoreover they are kind to the skin which is an essential aspect for therange of applications of clinical thermometers.

Where the additional structures of the thermally insulative meanscomprise air chambers, it may be convenient to provide several airchambers that are subdivided by fin members extending radially to theaxis of the base body claim 7). While on the one hand this provides forsufficient flexibility of the thermally insulative means conveying apleasurable feeling to the user, sufficient stability is imparted to thethermally insulative means in any direction on the other hand in orderto make sure that the air chambers maintain dimensions sufficient forthermal insulation also in compressed condition. Moreover, the finmembers may be formed of foamed plastic material (claim 8) in order tomaintain the thermally insulating properties and prevent the formationof heat transfer bridges. Where applicable, the fin members may haveapertures to connect adjacent air chambers in a fluid relationship toeach other and hence increase the flexibility using a certain dampingeffect.

Preferably, the window of the radiation thermometer is formed by awindow film transparent to infrared radiation or the actual window ofthe radiation thermometer is covered with such a film (claim 9); in oneembodiment, this window film may blend smoothly with a flexible outerfilm of the thermally insulative means covering the base body. Tostabilize the protective cap, a holding device according to claim 10 maybe utilized, for example, in the form of an annular body (claim 11)which is attachable, for example, to the rim of the base body (claim 12)and keeps the film smooth.

According to the features of claim 13 ease of manufacture of theprotective cap results because it is not necessary to cover the windowarea during application of the additional structures, but rather, it isequally equipped with thermally insulating material. It is onlysubsequently that the window is formed by hot pressing, hot stamping orcold stamping. In this process, the air chambers and the foamed plasticmaterial are pressed in such fashion that nearly clear transparentwindows are produced.

As preferred material for the base body and the window, polyethylene(PE) or polypropylene (PP) is utilized (claim 14). As preferred materialfor the additional structures serving as thermally insulative means inthe form a thermally insulating foamed plastic, polyethylene (PE),polyvinyl or polyurethane (PU) is utilized, for example (claim 15).

According to a second invention, the object of the present invention isattained by the features of claim 17. In this solution, the protectivecap, rather than having a base body, is fabricated only from a thermallyinsulating material such as foamed plastic or from a plastic materialhaving air chambers. The window's requisite thickness and transparencyto infrared radiation are then obtained by hot stamping or cold stamping(claim 18).

Further details and features of the present invention will becomeapparent from the subsequent description of embodiments with referenceto the accompanying drawings. In the drawings,

FIG. 1 is a section taken along the axis of an infrared optic system ofa radiation thermometer having a protective cap of the present inventioninstalled thereon, with the thermally insulative means of the protectivecap being formed of foamed plastic;

FIG. 2 is another sectional view of a protective cap in which thethermally insulative means of foamed plastic is provided only in theforward portion of the protective cap;

FIG. 3 is a sectional view of a protective cap in which the thermallyinsulative means is formed by air chambers;

FIG. 4 is a section of the protective cap taken along the line I—I ofFIG. 2; and

FIGS. 5 to 7 are various sections taken along the line II—II of FIG. 3perpendicularly to the axis of the protective cap, illustrating variousinner structures of the protective cap or the thermally insulativemeans.

As illustrated in FIG. 1, a protective cap 2 is installed on the forwardend of a temperature measurement probe 30 of an infrared radiationthermometer 1 suitable for use as a clinical thermometer 1 in order toprotect the probe 30 against contamination and, in addition, to providefor thermal insulation when the probe is inserted into a body cavity 31.In FIG. 1, the body cavity 31 is an ear canal of a person's ear 32 whichis, however, only shown schematically.

To take a person's body temperature, the temperature measurement probe30 is introduced into the ear canal 31 of a user's ear 32. In theabsence of a protective cap 2 of a radiation thermometer, the infraredradiation emitted by the tympanic membrane (not shown) and the ear canal31 passes through a window 3 transparent to infrared radiation in therelevant measurement range at the forward end of the temperaturemeasurement probe 30 and is directed, through an infrared waveguide 5extending coaxially with the axis 6 of the temperature measurement probe30 or the protective cap 2 when mounted thereon, to an interferencefilter 7, entering an infrared sensor 8. The temperature increaseproduced in the infrared sensor 8 results in an electrical outputvoltage from which the radiation temperature is derived through anevaluation unit not shown in greater detail, which temperature isindicated to the user as by means of a digital indicating means (notshown) which is accommodated in the housing 9 illustrated onlyschematically. As becomes apparent from FIG. 1, the waveguide 5 and theinfrared sensor 8 with the filter 7 have one end thereof held in amounting structure 10 which may be manufactured from metal, while theirother end is held by a tube 4 of the temperature measurement probe 30,which tube is a push-fit on the housing 9. The tube 4 is preferablyfabricated from plastic.

The tube 4 extends slightly conically towards its free end where thewindow 3 is integrally formed, having a stepped tapered end portion 11corresponding at its end to the outside diameter of the infraredwaveguide 5. By virtue of this tapered end portion 11, the clinicalthermometer is suitable for use on both children who have a relativelynarrow ear canal 31 and adults who have a wider ear canal 31.

As shown in FIG. 1, the installed protective cap 2 includes athin-walled tubular base body 12 tapering conically towards its free endand made from a plastic material. In this embodiment, a foamed plasticmaterial 13 serving a thermally insulating-function is affixed to theoutside of the base body 12. In a second embodiment which is, however,not shown here, the base body 12 is dispensed with entirely, theprotective cap 2 then being only comprised of foamed plastic material 13or forming a honeycombed air chamber structure.

At its upper free frontal end 14, the protective cap 2 is closed off byan infrared window 15 that is formed of a thin film transparent toinfrared radiation in the radiation range relevant for temperaturemeasurement. In FIG. 1, the film forms the base body 12 or is affixed tothe base body 12 as a separate member, as by weaving. Where theprotective cap is made of foamed plastic only, the film of the window 15is formed out of the foamed plastic by hot stamping or pressing.

Because of the requirement for such a film 15 to be very thin in ordernot to affect the measurement result by the material's naturalemissions, if any, a problem may present itself in the securing of sucha film to the frontal end 14 of the protective cap 2 without wrinklesbeing formed. To accomplish this, the embodiment shown makes provisionfor a holding ring 26 which is also shown in the embodiment of FIGS. 2and 3 and which is clamped upon the leading edge of the base body 12 oris injection-molded with the protective cap 2 in one integral piece. Theholding ring 26 may also be made of a different material of higherstrength.

In FIG. 1, the protective cap 2 terminates at its lower end in anannular flange 16 engaging in a clamping or snap-action fashion with theouter wall of the temperature measurement probe 30, thereby providing astiffening and centering function for the protective cap 2. On theinside of the flange 16 and/or on the outside of the tube 4 respectiveprojections and/or recesses, not shown, may be provided, enabling theprotective cap 2 to hook onto the outside of the tube 4 in the area ofthis flange 16 to thereby ensure a secure seat of the protective cap 2on the temperature measurement probe 30. The flange 16 serves at thesame time the function of improving manipulation of the protective cap2, enabling the user to grasp the cap by its flange 16 and install itover the forward end of the temperature measurement probe 30; bygripping it by the annular flange 16, the protective cap 2 readilydisengages again from the projections or recesses.

The thermally insulating foamed plastic material 13 of the protectivecap 2 of FIG. 1 has its maximum wall thickness approximately mid-waybetween the frontal end 14 and the annular flange 16. At least in itsupper portion which covers the tapered end portion 11 of the tube 4, itis desirable for the base body 12 to exhibit a certain flexibilityenabling it to deform towards the axis 6 such as to be almost engageablewith the outer wall of this end portion 11 of the tube 4, particularlyon insertion into a narrow ear canal such as a child's. When thetemperature measurement probe 30 of this thermometer 1 with theprotective cap 2 installed is inserted into a wide ear canal, the basebody 12 remains approximately in the position shown in FIG. 1, in whichcase only the elasticity of the soft foamed plastic material 13 and thepenetration depth of the temperature measurement probe 30 in the earcanal 31 perform an adaptation to the ear canal.

However, the possibility also exists to dimension protective caps 2 suchthat their base body 12 has an outer shape as predetermined by the tube4. Preferably, such protective caps 2 with such a tapered end can beinstalled on the thermometer 1 only if the thermometer 1 is used fortaking a child's temperature. In this event, there is no need to makeallowance for a free space 17 between the outside of the end portion 11of the tube 4 and the inside of the base body 12.

The thermally insulative properties of the foamed plastic material 13prevent the transfer of heat from the ear canal 31 which is at bodytemperature to the tube 4 which is, as a rule, cooler, such heattransfer would otherwise entail the risk of an insufficiently accuratetemperature reading. In consequence, apart from preventing contaminationof the window 3 and the outside of the tube 4, the thermally insulativeprotective cap 2 enhances the accuracy of temperature measurement withthe thermometer 1, hence avoiding measurement errors introduced due tothe transfer of heat from the ear 32 to the tube 4. For sanitaryreasons, the protective cap 2 should be replaced after each measurement.

FIG. 2 shows an embodiment of the protective cap 2 in which thethermally insulative means in the form of the soft, pliant foamedplastic material 13 is only provided in the tapered forward portion,whilst the lower half of the base body 12 which terminates in theannular flange 16 is left uncoated, that is, bare. It may be sufficientto apply the thermally insulating material only to the forward end ofthe base body 12 because it is substantially the forward end portion ofthe protective cap 2 that comes to rest against an ear canal 31.Attention should be paid to make sure that the thermally insulativemeans contain a significant amount of air. For this purpose, a foamedplastic material 13 with wide pores may be utilized, preferably a foamedplastic 13 with closed pores, so that major contaminants are preventedfrom settling in the foamed plastic material.

Another possibility of providing on the outside of the base body 12 athermally insulative means containing a significant amount of air isillustrated in FIG. 3. In this embodiment of the protective cap 2 whichhas essentially the same cross-sectional shape as the protective cap 2of FIG. 1, an air chamber 18 bounded from outside by a further film orwall 33 is provided on the outside of the base body 12. The elasticityof such a protective cap 2 is adjustable by the pressure applied forfilling the chamber 18 with air on the one hand, and by the elasticityof the wall 33 and the base body 12 themselves on the other hand.

The protective cap 2 may have thermally insulative means both in theform of foamed plastic material and in the form of air chambers.Adjoining the outside contour of the foamed plastic body 13 in downwarddirection is the outer wall 19 of a film combining with the base body 12to form a lower air chamber 20, so that the thermally insulative meansin the upper portion is the foamed plastic material 13, whilst in thelower portion it is formed by one or several (shown in broken lines) airchambers 20.

FIGS. 5 to 7 illustrate schematically various sections through theprotective caps 2, showing various possibilities for the internalstructure in the form of both foamed plastic materials and air chambers,or as combinations of both approaches to function as thermallyinsulative means. As FIG. 4 shows, it should be understood that thethermally insulative means may be designed in the form of an enclosedfoamed plastic body covering the outside of the base body 12, inaccordance with the embodiment of FIG. 1 (continuous) and FIG. 2 (in theupper portion only), or as a circumferential air chamber 18 inaccordance with the embodiment of FIG. 3.

However, the possibility also exists to cover the base body 12 withfoamed plastic fins 22 (FIG. 5) spaced uniformly apart on the basebody's circumference and being compressible as the thermometer 1 isintroduced in the ear canal 31. The free spaces 34 between the fins 22,whereof four are provided in the embodiment of FIG. 5, then combine withthe ear canal 31 (FIG. 1) to form individual air chambers 34. The fins22 may also be fabricated from a foamed plastic material selected in itsstrength such as to provide for adequate stiffening of the air chambers34, thereby preventing the outer wall 24 which bounds the air chambers34 from resting against the base body 12, while yet being soft andconsequently elastic enough to convey a pleasant feeling to the user asthe thermometer is inserted in the ear canal.

A further modification is illustrated in FIG. 6. In this modification,the outer wall 24 is connected to the base body 12 by thin,membrane-type fins 25 separating the air chambers 18 from each other. InFIG. 6, a total of eight fins 25 are provided, resulting in a total ofeight separate air chambers 18 distributed on the outer circumference ofthe base body 12. To additionally enhance user comfort, the fins 25 mayinclude apertures not shown, so that adjacent air chambers 18 are influid communication with each other to enable a pressure balance to beaccomplished between adjacent air chambers 18 and hence improve themating engagement with the ear canal 31.

FIG. 7 shows a further embodiment in which the protective cap 2illustrated in FIGS. 1 and 2 has the added provision of a furtherthermally insulative means 23 equally made of foamed plastic, forexample, which is affixed to the inside of the base body 12.

In summary, the protective caps as illustrated in the Figures afford thefollowing advantages:

-   -   The protective cap 2 diminishes the adverse effect of heat input        into a clinical thermometer, thereby improving the measurement        precision of the thermometer 1 or enabling the use of a smaller        (or simpler and less costly) thermometer optics with reduced        heat insulation and reduced thermal mass.    -   The protective cap 2 reduces cooling of the ear canal 31 during        measurement, thereby enhancing the accuracy of measurement of        the thermometer 1 or omitting the need for corresponding        compensations.    -   Due to the reduced cooling of the ear and the soft, elastic        protective cap 2, the measurement is appreciably less        discomforting for the user, particularly for children.    -   The soft outside of the protective cap 2 reduces the risk of        personal injury.    -   Used in combination with a clinical thermometer, the protective        cap 2 described makes it possible to determine the temperature        of children and adults alike speedily without causing pain.        Owing to its deformability, the protective cap 2 is capable of        conforming itself to different diameters of ear canals 31,        enabling an optimum penetration depth and centering of the        thermometer 1 in the ear canal 31.

Moreover, the use of protective caps 2 having different outsidediameters, for example for children and adults, on the same thermometer1 is possible.

The integrable holding ring 26 enables the window 3 or the window film15 of the protective cap 2 to be tensed in a uniform, defined fashionresulting in a uniform transmission. Any undefined tension of the window3 during mounting of the protective cap 2 is thus avoided.

1. A disposable protective cap for a temperature measurement probe of aninfrared radiation thermometer introducible into a body cavity, thedisposable protective cap shaped to fit the body cavity and having aproximal end engaging the temperature measurement probe and a frontaldistal end defining a longitudinal central axis therebetween, the distalend terminating in an opening closed by a window transparent to infraredradiation, comprising: a base body forming an inner wall of saiddisposable protective cap; and an outer wall spaced radially apart fromsaid inner wall, said outer wall being permanently attached to the innerwall so as to define at least one airtight chamber between the outerwall and the inner wall.
 2. The protective cap as claimed in claim 1,further comprising a soft, porous foamed plastic material disposedbetween the inner wall and the outer wall.
 3. The protective cap asclaimed in claim 1, characterized in that the at least one air chamberis formed by foamed plastic having closed pores.
 4. The protective capas claimed in claim 1, characterized in that the at least one airchamber has its outside close to the body cavity bounded by a flexiblefilm.
 5. The protective cap as claimed in claim 1, characterized in thatthe at least one air chamber has its outside bounded by a flexible outerfilm fabricated from plastic.
 6. The protective cap as claimed in claim1, characterized in that the window is formed of a window filmtransparent to infrared radiation.
 7. The protective cap as claimed inclaim 6, characterized in that the window film is stretched tight by aholding device.
 8. The protective cap of claim 1, wherein the distalseal is located at or near the distal end of the base body.
 9. Theprotective cap of claim 1, wherein the outer cover has an outwardlyconvex shape with respect to the longitudinal axis.
 10. The protectivecap of claim 1, wherein the air chamber is separated into a plurality ofchambers.
 11. The protective cap of claim 1, wherein the plurality ofair chambers are defined by at least one fin member.
 12. The protectivecap of claim 1, wherein the distal end of the base body includes a foaminsulating member.
 13. The protective cap of claim 1, wherein the outerwall is made of plastic selected from the group consisting ofpolypropylene, polyvinyl, and polyethylene.
 14. The protective cap ofclaim 1, wherein the base body is flexible and deforms towards thelongitudinal axis when the protective cap is inserted into and contactsthe body cavity.
 15. A disposable protective cap for a temperaturemeasurement probe of an infrared radiation thermometer introducible intoa body cavity, the disposable protective cap shaped to fit the bodycavity and having a window transparent to infrared radiation, thedisposable protective cap including a proximal end engaging thetemperature measurement probe and a frontal distal end defining alongitudinal central axis therebetween, comprising: base body forming aninner wall of said disposable protective cap; and an outer wall spacedradially apart from the inner wall, the outer wall being permanentlyattached to the inner wall so as to define at least one airtight chamberbetween the outer wall and the inner wall, and the at least one airchamber is subdivided by a plurality of fin members.
 16. The protectivecap as claimed in claim 15, wherein the fin members are formed of foamedplastic material.
 17. The disposable cap of claim 15, wherein the finmembers are connected between base body and outer wall.
 18. Thedisposable cap of claim 15, wherein the fin members are longitudinallyoriented.
 19. The disposable cap of claim 15, wherein the fin membersare made of foamed plastic.
 20. The disposable cap of claim 15, whereinthe fin members are thin, membrane-type fins.
 21. The disposable cap ofclaim 15, wherein the fins further comprise a plurality of aperturesthat fluidly connect the air chambers to balance the pressure betweenadjacent air chambers.
 22. The protective cap of claim 15, wherein theouter cover has an outwardly convex shape with respect to thelongitudinal axis.
 23. A disposable protective cap for a temperaturemeasurement probe of an infrared radiation thermometer introducible intoa body cavity comprising: a generally conical hollow base body of thedisposable protective cap having a proximal end and a free frontaldistal end defining a longitudinal central axis therebetween, the distalend terminating in an opening closed by a window transparent to infraredradiation, the proximal end terminating in radially outward projectingannular flange releasably engaging the temperature measurement probe; aflexible outer wall spaced radially apart from the base body; a proximalcircumferential seal permanently joining the base body and the outerwall at or near the proximal end of the base body; a distalcircumferential seal permanently joining the base body and the outerwall at or near the distal end of the base body, the proximal and distalseals defining at least one annular air chamber between the base bodyand the outer wall to thermally insulate the temperature probe from thebody cavity, wherein the base body, outer walls, and proximal and distalseals form a structurally self-supported protective cap that isremoveable from the temperature measurement probe and disposable. 24.The protective cap of claim 23, wherein the outer cover has an outwardlyconvex shape with respect to the longitudinal axis.
 25. An apparatuscombination of a temperature measurement probe of an infrared radiationthermometer and removable disposable protective cap therefor formeasuring body temperature, the combination comprising: a substantiallyconical temperature measurement probe for insertion into a body cavity;and a self-supporting disposable protective cap including: (a) a basebody shaped to fit the body cavity and having a proximal end releasablyengaging the temperature measurement probe and a frontal distal enddefining a longitudinal central axis therebetween, the distal endterminating in an opening closed by a window transparent to infraredradiation; and (b) an outer wall spaced radially apart from the basebody, the outer wall defining at least one airtight annular air chamberbetween the outer wall and base body to thermally insulate thetemperature measurement probe from the body cavity.
 26. The apparatuscombination of claim 25 wherein the at least one annular air chamber ispressurized with air.